The present invention disclosed herein relates to an optical coupler and an arrayed-waveguide grating structure including the same, and more particularly, to an optical coupler having a self-focusing region and an arrayed-waveguide grating structure including the same.
An optical element for muxing/dumuxing of a signal in optical communication fields and photonic integrated circuit (PIC) fields may include a arrayed-waveguide grating (AWG), an Echelle grating, a ring filter or a Mach-2ehnder interferometer. Among them, the AWG is a wavelength division multiplexer (WDM) device which is the most widely used. As the AWG, a silica-based AWG and a silicon or InP-based AWG has been studied. Here, the silicon and the InP have a larger refractive index than that of the silica.
If a material having a large refractive index is used, a curvature radius thereof becomes smaller, and an optical loss is minimized, and thus a size of the AWG device may be reduced. A general insertion loss of the AWG may be about 3 dB, and thus, how to reduce the insertion loss of the AWG is very important task. The insertion loss of the AWG is caused by a slab waveguide, couple structures between the arrayed-waveguides, and a waveguide loss.